Electric discharge device



Jan. 27, 1953 E. LEMMERS ELECTRIC DISCHAiRGE DEVICE Filed June 5, 1946 'INVENTOR: EUGENE LEMMERS, BY mil/WW HIS ATTORNEY Patented Jan. 27, 1953 ELECTRIC DISCHARGE DEVICE Eugene Lemmers, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application June 5, 1946, Serial No. 674,444

8 Claims. 1

This invention relates to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to improvements in the starting strip used thereon.

In the past in order to facilitate starting of the discharge in an electric discharge device starting strips were used to distort the electrostatic fields and to neutralize the effect produced by wall charges on the interior of the gas discharge envelope. Selective adsorption of certain ions or electrons clinging to the walls of the envelope was especially prevalent in devices employing a hot and glowing filamentary electrode. These starting strips were usually made of materials such as silver, aluminum, or bronze paint which by rubbing or abrasion action wipe or were off or were destroyed or become non-conductive when exposed to high temperature, for example that temperature necessary for proper sealing operations.

An object of my invention is to provide new and improved conductive starting strips for controlling electric discharge device operation.

Another object of my invention is to provide a new and improved composition which will adhere firmly to the glass wall of the envelope at temperatures above and below the glass fusion point.

A further object of my invention is to provide a new and improved composition embodying an infusible non-reactive component which will remain as a porous mass at temperatures above the glass fusion point.

A still further object of my invention is to provide a method of forming a conductive starting strip on a vitreous envelope of an electric discharge device.

Further features and advantages of my invention will appear from the following detailed description of species thereof.

In the drawing, Fig. 1 is a side elevation partly in section of the discharge device I therein comprising an elongated tubular or cylindrical envelope 2 having sealed into the ends thereof leadin wires 3, 4 and 5, 6 electrically connected to the electrodes, such as thermionic electrodes 7 and 8 respectively. Bases 9 and It], the type commonly used in the lamp industry, are formed with a pair of contact terminals or pins l I, I2 and I3, I4 respectively to which the lead-in wires 3, 4 and 5, 6 are respectively connected. Suitable provisions may be made, not shown, which connect the contact terminals or pins to a source of electrical energy for starting and maintaining the gaseous discharge between two electrodes and also for heating the electrodes if necessary,

whereby they are brought to a glowing and emitting temperature. The thermionic electrodes 1 and 8 are each herein illustrated as comprising a coil, preferably in the form of a coiled coil of tungsten wire activated with the usual mixture of barium and strontium oxide. The envelope 2 contains an ionizable medium. This ionizable medium may comprise a rare gas like krypton, neon, argon or mixtures thereof at a pressure of a few mm. and a small quantity of mercury which during operation of the lamp has a low pressure of the order of 10 microns. A quantity of mercury which may be in excess of that vaporized during operation of the device is indicated by a drop l5 inside the envelope 2. The device I may be a low pressure positive column lamp of the fluorescent type with a suitable phosphor which under the influence of an electric discharge through the ionizable medium produces fluorescence.

On the outside of the envelope 2, directly connected to the lead-in wire 3, and terminating in close proximity to the opposite end of the envelope, I provide a starting strip l 6 of conductive composition and embodying ingredients which will adhere to the glass and remain porous at temperatures above and below the glass fusion point. More particularly, I provide a composition for use with a vitreous envelope which will after heat treatment at temperatures above the glass fusion point result in a strongly adherent porous film containing metallic particles evenly distributed throughout. The composition essentially comprises a conductive ingredient, a bonding agent which may fuse below the temperature to which the discharge device is subjected during its manufacture, and a carrier or filler agent the fusion temperature of which is above that of the bonding agent and which assures and maintains the desired porosity of the composition after application to the discharge device. This starting strip may be either inside or outside the glass receptacle and means may be provided for connecting it to both ends, or it may be desirable to permit the starting stripto float, that is the starting strip is projected along the length of the discharge device and in close proximity to the ends thereof without connection to any electrode.

My invention relates to improvements in starting strips for electric discharge devices and lamps,-

and to improvements in the materials used therein and methods of manufacture and application to the device and lamps. More particularly, my invention relates to improvements in starting strips of the nature disclosed and claimed in a patent application Serial No. 660,093 of Jonathan Force, which was filed April 6, 1946, now Patent 2,491,854, and assigned to the assignee of this application. Generally speaking, my invention relates to improvements in such starting strips, which improvements are not disclosed in the aforementioned application, but which may be incorporated in the starting strip material therein disclosed. I provide a starting strip construction and material or composition thereof which has the desirable conducting and wearing qualities, and in which the final state of the material after being applied to the envelope is predetermined or controlled by the use of carrier or filler ingredients such as beryllium oxide, clay, aluminum oxide or similar materials which produce a desired or required porosity whereby the material or composition aifords the required conductive characteristics and is readily adapted for working at high temperatures during sealing operations performed on a device or lamp during its manufacture.

Generally speaking, I effect these desired results by means of a compound comprising ingredients which when combined together in the right proportions and applied to a glass envelope adhere to the glass and remain porous and conductive at temperatures above and below the glass fusion point. For example, this conductive substance, as disclosed in the before mentioned pending application Serial No. 660,093, may be a paste containing 1050 grams of silver oxide, 600 cubic centimeters of methyl alcohol, 840 cubic centimeters of glycerin, 450 grams of lead borate, and

in addition thereto per cent by weight of beryllium oxide. The beryllium oxide is used as the infusibl'e non-reactive carrier or filler material. It maintains a porous structure at temperature above and below the glass fusion point. Accordingly, if heat treatment below the glass fusion point is applied to a starting strip made of this compound the lead borate frits to the glass envelope and in combination with the beryllium oxide forms a porous body through which the reduced metal is dispersed. If the temperature is raised above the glass fusion point the lead borate melts and flows into a glassy non-porous material and the reduced metal and lead borate are evenly dispersed through the beryllium oxide which retains its porous structure at this elevated temperature. Thus, by combining an infusible non-reactive material with a conductive composition a conductive path is obtained which may be subjected to temperatures above the glass fusion point and by this means secure the continuity of the starting strip. Generally speaking the resistance of this starting strip is of low ohmic value usually to 100 ohms.

Application of this composition to the glass envelope 2 may be perfected either before or after the envelope is coated with phosphor and may be applied in any of the well known methods such as painting, squirting the material from a nozzle, or applying by means of a thin rubber roller. The viscosity, thickness, or stickiness of the composition maybe varied to fit the type of application by means of a suitable diluent such as methyl alcohol.

What I claim as new and desire to secure by Letters Patent of the United States is:

i. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a porous composition fritted to the said envelope and containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope and admixed with particles of a solid insulating filler material which has a fusion point materially above that of the vitreous envelope whereby it retains its porous structure at temperatures above the fusion temperature of the vitreous envelope, and metallic particles evenly distributed throughout the said porous composition and in physical contact giving electrical conductivity to said starting strip.

2. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a porous composition fritted to the said envelope and containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope and admixed with particles of a solid insulating filler material of the group consisting of beryllium oxide, clay and aluminum oxide whereby it retains its porous structure at temperatures above the fusion temperature of the vitreous envelope, and metallic particles evenly distributed throughout the said porous composition and in physical contact giving electrical conductivity to said starting strip.

3. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a porous composition fritted to the said envelope and containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope and admixed with particles of a solid material consisting of beryllium oxide whereby it retains its porous structure at temperatures above the fusion temperature of the vitreous envelope, and metallic particles evenly distributed throughout the said porous composition and in physical contact giving electrical conductivity to said starting strip.

4. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a porous composition fritted to the said envelope and containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope and admixed with particles of a solid insulating filler material which has a fusion point materially above that of the vitreous envelope whereby it retains its porous structure at temperatures above the fusion temperature of the vitreous envelope, and metallic silver particles evenly distributed throughout the said porous composition and in physical contact giving electrical conductivity to saidstarting strip.

5. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a porous composition fritted to the said envelope and containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope and admixed with particles of a solid insulating filler material of the group consisting of beryllium oxide, clay and aluminum oxide whereby it retains its porous structure at temperatures above the fusion temperature of the vitreous envelope, and metallic silver particles evenly distributed throughout the said porous composition and in physical contact giving electrical conduc tivity to said starting strip.

6. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a porous composition fritted to the said envelope and containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope and admixed with particles of a solid insulating filler material consisting of beryllium oxide whereby it retains its porous structure at temperatures above the fusion temperature of the vitreous envelope, and metallic silver particles evenly distributed throughout the said porous composition and in physical contact giving electrical conductivity to said starting strip.

7. The method of forming a porous conductive starting strip on the vitreous envelope of an electric discharge device which comprises forming a paste containing a bonding agent of lead borate having a fusion temperature below that of the vitreous envelope, an insulating filler material of the group consisting of beryllium oxide, clay and aluminum oxide which has a fushion point materially above that of the vitreous envelope, a reducible metallic compound consisting of silver oxide and a reducing agent for said metallic compound, applying said paste to said envelope as a strip, heating said envelope and strip to a temperature below the fusion point of the envelope but sufiicient to efiect fritting of said bonding agent to said envelope and reduction of said metallic compound to metallic particles evenly distributed throughout the strip and in physical contact, and heating at least a portion of said envelope and strip to a temperature above the fusion point of the envelope whereby the said bonding agent melts and flows into a glassy nonporous material but the filler material retains its porous structure.

8. The method of forming a porous conductive starting strip on the vitreous envelope of an electric discharge device which comprises forming a paste containing a bonding agent consisting essentially of lead borate, an insulating filler material consisting of beryllium oxide, silver oxide and a reducing agent for said silver oxide, applyin said paste to said envelope as a strip, heating said envelope and strip to a temperature below the fusion point of the envelope but suflicient to eifect fritting of said lead borate to said envelope and reduction of said silver oxide to silver particles evenly distributed throughout the strip and in physical contact, and heating at least a portion of said envelope and strip to a temperature above the fusion point of the envelope whereby the said lead borate melts and flows into a glassy nonporous material but the berryllium oxide retains its porous structure.

EUGENE LEMMERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,915,019 Ewest June 20, 1933 1,922,221 Steenbeck et al. Aug. 15, 1933 2,053,879 Spanner Sept. 8, 1936 2,094,647 Freitag Oct. 5, 1937 2,146,579 Inman Feb. 7, 1939 2,405,089 Craig July 30, 1946 2,462,336 Ruff Feb. 22, 1949 

